This invention relates to a reconnaissance pod within which a sensor is mounted, and, more particularly, to such a reconnaissance pod that is mountable to an aircraft.
An optical sensor receives radiated energy from a scene and converts it to an electrical signal. The electrical signal is provided to a display or further processed for pattern recognition or the like. Optical sensors are available in a variety of types and for wavelengths ranging from the ultraviolet, through the visible, and into the infrared. The optical sensors generally employ a photosensitive material that faces the scene and produces an electrical output responsive to the incident energy. The photosensitive material and remainder of the sensor structure are rather fragile, and are easily damaged by dirt, erosion, chemicals, or high air velocity. In service, the sensor is placed behind a window through which it views the scene and which protects the sensor from such external effects. The window must be transparent to the radiation of the operating wavelength of the sensor and must resist attack from the external forces. The window must also permit the sensor to view the scene over the specified field of regard.
In one sensor application, the sensor is enclosed in a pod that is affixed to the underside of an aircraft, and the window is provided through the wall of the pod. The sensor is directed generally downwardly but may be moved from side to side (termed the azimuthal direction) to view a scene on either side of the aircraft""s ground path and also to permit the sensor to remain aimed at a specific portion of the scene when the aircraft banks. The window must be large enough to view the required field of regard.
Windows extending over a large azimuthal angle, such as the range of xe2x88x9230 degrees to +30 degrees relative to the aircraft centerline, are expensive to produce and may suffer from irregularities that degrade the image quality at particular pointing angles. The shutter system required to protect the window when the sensor is not in use is large, heavy, and complex. In some cases, the window may be segmented into a number of panes to reduce the cost and the presence of irregularities, but the problems remain to some extent and there are problems introduced by the segmentation of the window.
There is a need for an improved approach to a sensor pod in which the window allows a large side-to-side field of regard of the sensor, but overcomes the problems with prior approaches. The present invention fulfills this need, and further provides related advantages.
The present invention provides a reconnaissance pod that may be carried below an aircraft. The reconnaissance pod allows a wide azimuthal field of regard of the sensor assembly in the pod, but utilizes a relatively small window which may be made of the highest optical-quality material to ensure high image quality of the sensor. No protective shutter system is required, reducing weight and complexity and also providing maximum usable space within the reconnaissance pod for the sensor assembly. The reconnaissance pod has a good aerodynamic shape and performance. The reconnaissance pod is less expensive to produce than a pod having a large window size. The reconnaissance pod is fully self-contained, except for electrical leads extending to the aircraft.
In accordance with the invention, a reconnaissance pod for viewing a scene comprises a structural backbone extending generally parallel to a pod axis, a forward housing affixed to the backbone, and an aft housing affixed to the backbone. The aft housing is spaced apart from the forward housing along the pod axis. A central housing is mounted between the forward housing and the aft housing. The central housing includes a central body, and a window through the central body and affixed to the central body. The window is controllably movable relative to the backbone between a first position and a second position.
Preferably, the central housing is substantially cylindrical having the pod axis as its cylindrical axis. The central housing is supported on the forward housing and on the aft housing, but not directly on the backbone. Desirably, the central housing is rotationally supported on the forward housing and on the aft housing, so that the window is rotatable about the pod axis. At least a portion of a sensor assembly is typically supported within the central housing.
In a preferred approach, the structural backbone also includes an attachment adapted for affixing the structural backbone to an aircraft mounting site. The forward housing and the aft housing are aerodynamically tapered. The forward housing may further comprise a radar transceiver, and a radome through which the radar transceiver transmits and receives a radar beam.
In one embodiment, a reconnaissance pod comprises a structural backbone extending generally parallel to a pod axis, a forward housing affixed to the backbone, and an aft housing affixed to the backbone, with the aft housing being separated from the forward housing along the pod axis. A central housing, mounted between the forward housing and the aft housing along the pod axis, includes a central body, a window through the central body and affixed to the central body, with the central body and the window together being substantially cylindrical about the pod axis. At least a portion of a sensor assembly is supported within the central housing from at least one of the forward housing and the aft housing. A rotational drive assembly comprises a forward support rotationally supporting the central body from the forward housing, wherein the forward support includes a forward bearing oriented to permit rotation of the central housing about the pod axis. The rotational drive assembly also includes an aft support rotationally supporting the central body from the aft housing, wherein the aft support includes an aft bearing oriented to permit rotation of the central housing about the pod axis. A controllable drive motor is operable to drive the rotation of the central housing about the pod axis on the forward bearing and the aft bearing.
In this configuration, the reconnaissance pod may be made with the forward and aft housing having tapered aerodynamic shapes, and the central housing is substantially cylindrical. This reconnaissance pod has excellent aerodynamics, introduces minimal drag to the aircraft, and does not introduce asymmetric drag to the aircraft.
Typically, the rotational drive assembly further includes a drive engagement, such as a cable drive engagement, between the drive motor and the central housing. There is a forward seal between the forward housing and the central housing, and an aft seal between the aft housing and the central housing. The forward bearing and/or the aft bearing may include an elastomeric mount to accommodate flexing of the backbone and thence the housing assembly during service.
During service, the sensor controller points the sensor to different azimuthal angles as may be required during the viewing of a scene. The azimuthal angle may be changed to view a different portion of the scene, or to remain trained on a single portion of the scene when the aircraft banks. The actuator that rotates the central housing is controlled to move the window, by rotating the central housing about the pod axis in the preferred embodiment, so that the window remains in the line of sight of the sensor to the viewed portion of the scene. The window itself may be made relatively small in azimuthal extent using this approach, so that the window may be made relatively inexpensively yet with high optical quality.
When the sensor is out of operation, the central housing and its window are rotated so that the window faces upwardly into the backbone. The window is thereby protected from damage due to external causes by the fuselage of the aircraft.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.